Technicians this weekend will hook up wires intended to prevent a repeat of a shorted-out circuit that scrubbed the mission's first launch attempt April 29.

A news conference Monday afternoon will update whether Endeavour is on track to launch a week later.

"We're getting close," Kennedy Space Center spokesman Allard Beutel said. "If it's not the 16th, it will be right around then."

The first attempt to launch Endeavour's 25th and final mission, commanded by astronaut Mark Kelly, whose wife, Rep. Gabrielle Giffords, D-Ariz., continues to recover from a gunshot wound to the head, was called off when heaters on a hydraulic-system fuel line failed to turn on.

Troubleshooting teams removed a power-distribution box from the orbiter's aft section and found a damaged fuse.

The box and a thermostat have been replaced, but engineers haven't determined if the cause of the electrical short is inside the switchbox or in wiring outside it.

To get around the latter problem, managers routed new wires between the box and the fuel-line heaters.

Once the wiring is completed, possibly this weekend, the heaters will be run for up to 30 minutes. Additional tests will make sure dozens of other functions powered by the new box are working properly.

While the launch date remains uncertain, NASA on Friday officially extended Endeavour's mission to the International Space Station from 14 days to 16. The shuttle will deliver spare parts and a $2 billion cosmic-ray detector.

The extension was expected, but NASA had previously planned to wait until after the mission got under way to approve it.

The extra time will help get some important maintenance tasks completed on the station, whose six-person crew has had its hands full in recent months with spacecraft coming and going.

Another vehicle departure is scheduled May 23. Three station residents, including American astronaut Cady Coleman, are heading home.

That will cut in half the crew available to support portions of Endeavour's mission, which includes four planned spacewalks. But NASA says the reduced joint crew won't impact the mission's goals.

If the May 16 launch date is confirmed, six Endeavour astronauts led by Kelly would return to Kennedy Space Center on Thursday and a three-day countdown would pick up Friday morning. Endeavour's earliest return to Florida would be June 1.

A May 16 launch would require NASA to again reschedule the space shuttle Atlantis' move into the Vehicle Assembly Building, which was tentatively planned that day.

But no decisions have been made yet pending Endeavour's progress, and Atlantis remains targeted to blast off on the final shuttle mission June 28.